Good idea
Lingering Fog health thingy
First Stage:
Hungry more often
Thirsty more often
Second Stage:
Dwarf tires more easily
Becomes a lazier dwarf
Third Stage:
(But depending on what the fog does (mutation, murder, husk, zombify, ghoulify etc) thing will be different.)
Mutation:small growths and increased/decreased abilties (but it would be rare for increased(more risk=more FUN))
Being worse/better at some jobs or fighting.
Murder: mild pain, vomiting occasionly.
Husk: skin is starting to go hard and turn light greyish blue (in my mind they look like this minus the pipe things)
Zombify:the dwarf may randomly attack other dwarves or eat meat more
Ghoulofy: skin starts going light green and dwarf attacks animals randomly.
Stage Four:
Mutation: Dwarf starts growing claws(a bonus) or other weapons (material is random, but stronger things are rarer for each weapon, like an addy hammer or copper claw) or increased metabolism (definatly not a bonus)
Murder: Random bleeding, pain, voting and if a dwarf is weak death.
Husk: Starts to turn greyish blue, and attacks things frequently also is good for a Spectre (send him out to pwnca seige)
Zombify: Starts limping, minor rot and attacks living things frequently and will be ignored by undead but can still attack them.
Ghoulify: skpSkin turns light green, stops doing jobs and wanders around aimlessly.
Final Stage:
All transformations complete.
Mutations don't make a dwarf leave your fort though.